He rubbed his hands together. 'Well, I've managed to track down Malcolm Broadbent, for starters. If you remember, he was our number one suspect. But it looks like we can rule him out, at least for the Holland Park murder. If his alibi stacks up, he was away visiting his mum in Hull.'

'Which leaves the other suspect...what's his name?'

'Yes, Mike Jennings. He's moved. At the moment I haven't been able to track him down. But I'm on the case, Sam.' He paused, gazing at her intently with his strange, pale eyes. 'Don't worry. I know what you think but I'm getting myself sorted. Really I am. I'm not going to fuck things up and let you down. Honest.'

She was tempted to say that he had already done that, but she stopped herself. He was smiling at her in a sheepish sort of way and he reminded her of a shaggy golden retriever, thumping its tail on the carpet, desperate to please. More than anything, she sensed his loneliness and, in spite of her irritation, she couldn't help but feel sorry for him.

She was saved the embarrassment of finding a suitable reply by the ringing of her mobile. Claire was at the other end, in Tesco's, asking what to buy for supper.

'I can't make up my mind,' Claire said, shouting over the general background noise. 'Do you fancy lasagne or shepherd's pie or macaroni cheese?'

'Either lasagne or macaroni cheese. We had the shepherd's pie when I last cooked and it wasn't that great.'

'I'll be going,' Turner said in the background, getting to his feet.

Donovan heard Claire's voice in her ear. 'Is that Mark? Do you want to ask him along?'

'No, it's not. Actually, hang on a sec. Hey, Simon,' she called after Turner, who was on his way out the door. 'Got any plans for tonight?'

He looked round. 'Only a date with Nicole Kidman. Nothing that won't keep.'

'Well, come over and have a bite to eat at our house. My sister Claire's cooking, or rather reheating something from Tesco's. I can't promise the Domestic Goddess but it should be edible.'

'That would be nice, thanks.' He hesitated. 'If you're sure...'

'Absolutely.'

She heard Claire's voice: 'Who's that? Who's Simon? Are you two being rude about my cooking?'

'Can I bring anything?' Turner muttered.

'Just yourself and some whisky, if that's what you fancy drinking.'

'Sam, are you listening to me?' Claire shouted. 'Who's that you're with?'

'Tell you later and there'll be one extra for dinner. Don't forget to get some wine.'

Liz sipped her mug of tea and gazed out of the kitchen window at the ominous dark grey sky. She had been cooped up inside for most of the day, sorting through various boxes of things that she had stored in the spare room of her brother's flat. She had been looking for her photo albums, but God only knew where they had got to, probably still at her mother's, or at least she hoped so. Instead, she had turned up a collection of old letters and postcards, an address book, and a diary from her first year at university which she had forgotten about. Leafing through it, she was carried straight back to that time, the sparse one-line entries reminding her, like everything else, of Rachel.

She had found a suitcase of old clothing, mainly jumpers and a couple of T-shirts going back at least a decade or more. Most of it was fit only for binning, as the moths had had a field day. But one particular dress caught her eye. It was vintage 1940s, black silk patterned with small pink and red flowers. The edges were fraying, the hem was coming down and there were a couple of small holes along one of the seams, but it was still pretty and she remembered buying it for only a few pounds in the Portobello Market almost twenty years before. Jeans and T-shirts had been her daily uniform at that age and it was the only dress she had been happy to wear; looking like a stick insect, nothing suited her, as far as she was concerned.

She stood up and took it over to the mirror on the wall, holding it up against herself, wondering if she could still fit into it. But it looked incredibly short, the waist too high; she must have grown since the last time she had worn it. She folded it carefully and put it back in the suitcase. She would worry about what to do with it later. Not knowing why she had hung onto it for so long, she was struck by how much everything had changed since those days.

Sitting on the floor all that time had made her feel stiff. She needed to get out, stretch her body and feel fresh air in her lungs. Running was something she had done since her teens and she had often gone with Rachel. Every Friday, they would take their bikes to Holland Park after school, dump them at the adventure playground and race each other on foot down the tracks until, hearts bursting, they would collect their bikes and go home, always stopping in a cafe on the way for a milky coffee, a Mars bar and a chat. It became a weekly ritual until they both went off to university. The cafe had long since gone out of business and been replaced by something more glitzy and upmarket, as suited the area which, in twenty years, had come up a very long way. At least the park remained more or less the same.

She hadn't been out running once since coming back to London. The weather had been so foul with all the snow and rain that she simply hadn't felt like it. But as she gazed out of the window, watching a woman jog slowly around the green rectangle of lawn in the communal gardens below, she decided it was time. She would go to Holland Park. Although wary after what had happened, she wanted to visit the place where Rachel had died. Somehow, she hoped it might help her find some peace. Maybe it would also bring her closer to Rachel again.

She went into her bedroom and changed into her tracksuit bottoms, T-shirt and fleece. She slipped on her running shoes, tied her hair back and picked up her iPod. It was already late and the park would soon be closing. She took the keys to her brother's car and drove the short distance up the hill to the park, leaving the car near the entrance. The notice board by the gates said that the park would close at four-thirty. She still had about twenty minutes to go, which should be ample.

Apart from a group of dog walkers gathered together on the main broad walk, chatting while their charges ran riot on the lawn below, the park was surprisingly empty for a Saturday. The sloping, muddy lawns and playing fields appeared peaceful and a light mist shrouded the dips and hollows of the grass, gathering in hazy drifts under the canopy of trees. Liz stopped by the tall, shiny black iron railings and gazed for a moment, trying to imagine how it all would have appeared the morning Rachel had died. Everything would have been white, covered by a thick blanket of snow. In the fading afternoon light, she found it hard to picture.

She walked for a few minutes, warming up, then started to jog slowly along the path beneath the south terrace, U2's 'With or Without You' pounding over her headphones. The song reminded her of university, hours spent with Rachel listening to music in her room, talking until late at night and drinking endless cups of tea and coffee.

The ruins of Holland House stood proud against the darkening sky. As she turned to look at the empty windows, wondering if, on that morning, Rachel had come this way, a sense of sadness overwhelmed her. Guilt was a terrible, insidious thing. It could eat you up. Would she ever get over it? Fighting back the tears, she pushed herself faster, past the orangery and up through the formal gardens towards the woodland area. She felt the thud of her feet on stone, then dirt and gravel, but she heard nothing over the music.

The light dimmed as she ran into the woods and it took a moment for her eyes to grow accustomed to the gloom. Dense evergreen shrubbery bordered the path on either side and the bare branches of the trees arched above her like fingers against the dark sky. She ran down the hill, following the track as it bent sharply to the left. After a minute or so, it opened up into a wide clearing, where several other paths met. A strand of blue and white police tape fluttered in the wind, one end tied to a tree.

She pulled up, paused the music and removed the earphones. She wanted to hear the real sounds of the place. Tartaglia had been vague about where exactly Rachel's body had been found, but it had to be somewhere close by. A high picket fence ran along the track on either side, separating it from the woodland area beyond. She assumed its purpose was to stop the public trampling over the ground and disturbing the flora and fauna, although the area inside was so dark and overgrown, she couldn't imagine any human wanting to set foot in there.

She felt in the pocket of her fleece and pulled out the pack of cigarettes and lighter that Tartaglia had left behind in her flat the other evening. She had no intention of taking up smoking again but she lit one anyway, hoping it would calm her nerves. A few benches were dotted around the clearing. Choosing one that was sheltered by an arbour of thick holly branches, she sat down. The air was cold and damp. As she exhaled, the smoke drifted away in front of her like a ghost. Something rustled close by in the undergrowth, a bird perhaps, rooting around amongst the dry leaves on the other side of the enclosure. Scanning the area, she saw another ribbon of police tape on the other side of the fence a little way along the path in the woodland area. She was about to get up and look when there was an eruption of flapping and squawking from a group of rooks high above in one of the trees, as though they had been disturbed by something.

Peering through the branches, she saw someone jogging along one of the tracks towards her. The light was so poor, it took her a second or two to tell that it was a man. He was nearly in the clearing when he slowed to a walk and stopped. He looked tall and well built and was wearing a dark anorak, the hood pulled up over his head so that she could only make out a pale oval of face. He was carrying something bulky in his hand and walked up and down the fence for a moment, as if searching. The rooks stirred again up in the trees and he looked quickly up and down the path, as though he was checking to see if anyone was coming. His movements were furtive and she kept very still, screened by the branches of the holly tree, hoping he hadn't seen her. With a final glance in both directions, he stepped through what looked like a hole in the fence, into the enclosure beyond, and disappeared behind a thicket of evergreen.

People used the park every day and there could be a perfectly innocent explanation. Maybe he had some sort of secret assignation, although she hadn't seen anyone else in that part of the woods. But his behaviour was still odd and she cursed herself for having left her phone in the car. She reached down and stubbed out her cigarette on the side of the bench and waited. After no more than a couple of minutes, the man re-emerged from the bushes. He was empty-handed as he jumped back through the hole in the fence and stood for a moment on the footpath staring into the enclosure, exhaling a cloud of steam. He wiped his forehead and mouth with the back of his hand, as though satisfied with whatever he had done, then took off at speed the way he had come.

As soon as he was out of sight, she got to her feet, curious to know what he had been doing. She felt cold from sitting still for so long and stamped her feet and stretched her arms and legs until the blood was flowing again. She walked over to the hole in the fence and, after a moment's hesitation, stepped through the gap into the woodland area. The ground was uneven and strewn with bracken and fallen branches. She pushed her way through the bushes and came to a small clearing, surrounded by tall holly trees. Something white lay in the middle of the rough grass. She went over to it and saw that it was a bunch of roses still in their paper wrapping. The buds were tightly furled and they were a deep, dusky red.

21.

Just after four o'clock in the afternoon, Tartaglia pressed the bell of Trevor Clarke's modern, semi-detached house in Wandsworth. Sally-Anne, Clarke's fiancee, opened the door, dressed in tight jeans, high heels and a blue tracksuit top, her long blonde hair tied back in a pony tail. She stood on tiptoe to kiss him, then let him pass. Clarke was sitting just behind her in a shiny, metallic red wheelchair.

'Great to see you, mate,' Clarke said, gliding forwards. Grinning, he clasped Tartaglia's hand, squeezing hard.

'You're looking pretty good, Trevor,' Tartaglia replied, looking him up and down. The last time he had been there, Clarke had been bedridden and painfully gaunt and pale. Although he was still thin compared to before the accident, he had filled out a little and the colour had finally returned to his long, craggy face. 'The macrobiotic diet seems to be working and I see you've got rid of that seventies moustache.'

Clarke shrugged. 'Sally-Anne insisted.'

'It tickled,' Sally-Anne said, with a giggle. 'Makes him look younger, don't you think?'

'It's a big improvement. He doesn't look like Tom Selleck anymore.'

'That's nice,' Clarke growled. 'What do you think of the chair? Lovely bit of kit, eh?'

Tartaglia studied it carefully. 'Lovely' wasn't the word he would have chosen, but he assumed it did the job. 'It looks like an office chair on a box, on wheels.'

'That's the way they design them these days.'

He shook his head. 'Design? At least it's safer than a motorbike.'

Clarke grinned again. 'It's nearly as fast and look, it's got all mod cons. Watch this.' At the touch of the joystick, the chair performed a variety of jerky manoeuvres. 'All I need now is satnav and I'll be back on the road and round to sort you lot out.'

'He's just like a child with a new toy,' Sally-Anne said.

'Well, it cost a bloody arm and a leg,' Clarke said, executing a pirouette. 'Might as well have some fun. Thought I'd better splash out and get the top of the range. They seem to think I might be in it for a while.'

'Stop showing off, Trevor, and let Mark pass, will you? You don't want to keep Dr Harper waiting.'

'Sorry. I was getting carried away. Let's get down to business.'

He spun around and led the way along the corridor and down a small ramp into the kitchen. Dr Angela Harper was sitting at the kitchen table, sipping something from a large mug.

'It's good of you to see me,' Tartaglia said, as she stood up and shook his hand with a cool, firm grip.

'Don't mention it. I'd do anything for Trevor here, and I'm naturally very interested to know of any developments in the Watson case.'

Her voice was pleasant and low, with a trace of a northern accent. She was wearing a charcoal grey trouser suit and was taller than he remembered. Her prematurely silver hair was cut into a neat bob, emphasising her broad, strong-boned face, and she wore no make-up apart from a slick of browny-pink lipstick.

'Let me take your things, Mark,' Sally-Anne said. 'You must be soaked. Would you like coffee or tea?

'No, I'm fine, thanks,' Tartaglia said, handing her his wet jacket and helmet.

'It's gone five,' Clarke said, zooming over to the table where he took his place at the head. 'I'm sure Mark would like something stronger.'

'Really, I'm fine, Trevor. I've got to go back to the office after this.'

Tartaglia sat down opposite Angela Harper. Rain was streaming down the window behind her, but through the misted glass he could just make out the back garden with its new, neat paving and square of lawn. A couple of children's bikes stood propped against the side wall next to a large covered barbecue, and it struck him how much life had changed for Clarke since Sally-Anne had appeared on the scene nine months before.

'If you're sure I can't get you anything, I'll leave you all to it,' Sally-Anne said, bringing a tall glass of iced water over to Clarke. 'I've got some chores to do upstairs and I want to make sure the boys keep quiet while you're working.'

As she spoke, small footsteps thundered across the ceiling above. The boys were her two sons from her previous marriage, who were now living with her and Clarke.

'She gets queasy if I start talking about anything to do with work,' Clarke said apologetically, as she raced out of the room. 'Doesn't like the mention of death, let alone the gory details.' He spread his hands out flat on the table. 'Anyway, Mark, this is your show. I'll try and keep out of it. I've given Angela the gist of the Holland Park murder but you ought to run through it, in case I left something out.'

Tartaglia outlined where they had got to in the case, adding the latest piece of news about the papers and poem found in Catherine Watson's flat. Sipping her drink, Harper took in the information without speaking. It was impossible to gauge her reaction. When he had finished, she put down her mug and folded her hands neatly in front of her.

'I can see why you're puzzled. I must say, I am too.'

'The MOs are very different,' Tartaglia said. 'The poem and the way the bodies were both positioned gives us a direct link but I'm struggling to see how the same person could have committed both crimes.'

Harper nodded slowly. 'It's not immediately obvious, I agree, although the two murders do have a couple of things in common. Let's start with the Catherine Watson case, which I'm more familiar with. As you know from the files, it seems very likely that Catherine Watson knew her killer and was specifically targeted. From the evidence we have, we also know that the killer was highly organised. The planning of the assault, down to the details of the equipment he brought with him his rape kit, if you like would have been very important to him, probably as much as the assault itself. It's all about ritual. This is first and foremost a sexually motivated crime. I also think it mattered to him very much that she was conscious throughout the ordeal. I imagine him talking to her, describing what he's going to do. He was turned on as much by the anticipation of what was to come, of her being aware and by her reactions and fear, as by the sex itself.'

'So he's a sadistic bastard as well as a pervert?' Clarke said, with a grimace.

She nodded. 'The crime is certainly sadistic. I'm sure he tortured her mentally and he certainly wounded her far more than he needed to. But more than anything, it's about control and empowerment, based on the ritual humiliation and subjugation of the victim while she's still alive. As I said, her being alive and responding to him would have been very important. But unlike many sexual killers, he's not a necrophiliac. Death itself is not a turn on.'

'Do you think it's important that Catherine Watson was a teacher?' Tartaglia asked, thinking also of Rachel Tenison as he spoke.

She smiled. 'He may have a specific grudge against teachers, but I think it's more about her role as a woman in a position of authority. Somewhere in his past he has been made to feel powerless or insignificant by a woman, or a series of women, and what he did to Catherine Watson was about reasserting himself. He controls life and he controls death. Although he's essentially a rapist, not a killer and the difference is important in terms of the profile.'

Clarke bit his lip and shook his head in disbelief.

'You don't agree, Trevor?' Tartaglia asked.

'He put the poor woman through hell and she ended up dead. I find it difficult to believe he hadn't meant to kill her.'

Harper nodded. 'I'll come on to that in a minute. The ordeal lasted several hours, but what's interesting is that in all that time, he shows no rage or frenzy or loss of control. He even feels secure and calm enough afterwards to tidy up and leave the flat as though nothing's ever happened. That's unusual and it tells us a lot about him.'

'What about the way the body was laid out?' Tartaglia asked, thinking again of Rachel, seeing the image that was burned on his mind of her body tied up in the snow.

'That's important too. Some sexual predators discard their victims like rubbish when they're done, but this one sees his as a trophy, rather like a big-game hunter. He displays her in a specific way for her to be found. He's sending a message.'

'She was hog-tied and kneeling down like she was praying,' Clarke said, unable to contain himself. 'What sort of message is that? Is he having a joke? Is he sticking his tongue out at us?'

'In a way, or at every woman who's made him feel small in the past. It's the final humiliation and it's a warning. If he'd put an apple in her mouth, I wouldn't have been at all surprised. He's saying that she is his thing, his chattel; he can do with her what he wants.'

'He's trying to depersonalise her?' Tartaglia asked, still thinking of Rachel Tenison and how her face was hidden.

'Yes. Although, going back to what I said before, by this point it didn't matter to him that she was alive or dead. Death isn't the issue here.'

'Poor woman,' Clarke muttered, and took a gulp of water.

'So you accept Malcolm Broadbent's account of how he found Catherine Watson's body?' Tartaglia asked, remembering Broadbent's statement and what Turner had said about it.

'I thought you told me Broadbent was a liar,' Clarke said to Tartaglia.

'That was Simon Turner's view.'

'Well I believed Broadbent,' Harper said, firmly. 'At least, I believed what he said about finding the body. He may have lied about other things, but you must remember he was put under a lot of pressure during the interrogation. I think he would have lied about the colour of his own eyes, he was so confused and upset. In my view, his account of his behaviour at the crime scene was psychologically consistent with his personality type.'

'What, you mean the way he fucked it up?' Clarke asked.

'I don't believe he had any idea of what he was doing, Trevor. He comes downstairs and finds the door to the ground floor flat open. He knocks, and when he gets no response he goes in and gets the shock of his life. A woman he respects and cares about, some might say even loves, is bound and gagged, kneeling stark naked on the floor for all to see. He hears her moan-'

'For Chrissake, she was dead,' Clarke protested.

'Could have been gas, Trevor,' Tartaglia said. 'The first time a body did that to me in the morgue, I nearly jumped out of my skin. Broadbent's just a layman. He wouldn't know what it was.'

Clarke nodded grudgingly. 'OK. Gas, imagination, whatever. Go on, Angela. I won't interrupt again.'

'So, Broadbent cuts off the bindings and carries her into her bedroom, lays her out on the bed and covers her with a blanket. He's screaming and shouting and calling out for help as he tries to revive her. It all makes perfect sense to me. From everything we know about him, he's a highly disorganised personality, with a below-average IQ. He had some pretty odd habits, I grant you, but I don't think he was capable of carrying out such a methodical and controlled attack and I told DCI Gifford that at the time.'

'That didn't come out in the closing report,' Tartaglia said.

Clarke waved his hand dismissively. 'Probably because it was overseen or written by Alan Gifford.'

'You know, if they'd treated Broadbent as a witness instead of a suspect, he might have remembered something useful,' Harper said, with feeling.

'Are you saying Gifford completely disregarded your profile and advice?' Tartaglia asked, surprised.

Harper raised her eyebrows and smiled, as though it wasn't the first time it had happened. 'This is off the record.'